An ECG monitor is a diagnostic instrument for providing a real-time or delayed display or a printed record of a patient's ECG waveform. The ECG monitor is typically interconnected with the patient via a set of electrodes and associated conductors commonly referred to as a patient cable. A defibrillator is a therapeutic instrument that is used to assist in curing certain cardiac irregularities, particularly ventricular and atrial fibrillation. The defibrillator is a therapeutic instrument that is used to assist in curing certain cardiac irregularities, particularly ventricular and atrial fibrillation. The defibrillator is typically interconnected with the patient via a set of large paddle electrodes and associated conductors, and operates to apply a high energy DC pulse to the patient via the paddle electrodes when appropriately triggered by an operator. The operator's decision to use defibrillation is typically based upon an examination of the patient's ECG waveform.
In one prior type of physiological instrument, an ECG monitor and a defibrillator are combined and electrically connected within a single housing. In such an instrument, circuitry is often provided to allow the ECG monitor to receive the ECG signal through the paddle electrodes that are normally associated with the defibrillator, rather than through the patient cable. Although the patient cable provides a better ECG signal, there is often an important speed advantage in using the paddle electrodes. Physiological instruments are also known in which the ECG monitor and defibrillator are modular units that are capable of operating either independently, or in an interconnected manner in which the defibrillator is mechanically and electrically connected to the ECG monitor.
A pacemaker is a therapeutic instrument that is connected to a patient through pacing electrodes and associated connectors, and operates to deliver a series of electrical pacing pulses to the patient. Each pacing pulse stimulates one heart contraction, and the pacing pulses are therefore delivered at a rate corresponding to the desired heart rate. A pacemaker may operate in either a nondemand mode, in which pacing pulses are delivered regardless of the patient's heart activity, or in a demand mode in which pacing pulses are only delivered if the patient's heart is not pumping properly. For demand pacing, an ECG monitor or its equivalent is required in order to monitor heart activity.